The invention relates to a tire with radial carcass reinforcement anchored in each bead to at least one bead wire, and comprising a crown reinforcement formed by at least two so-called working plies, superposed and made of wires or cables which are parallel to each other in each ply and are crossed from one ply to the other, forming angles of at most 45.degree. in absolute value with the circumferential direction of the tire.
French Application FR 94/15 736, which has not hitherto been published, relates to a tire as described above, and more particularly to a heavy truck tire, the ratio of the height above rim H to the maximum axial width S of which is at most 0.60. Said application, in order to improve the life of the crown reinforcement of such a tire, and also the regularity of wear of the tread thereof, requires an architecture of the crown reinforcement characterized by the combined presence in said reinforcement of an axially continuous ply formed of inextensible cables forming an angle of at least 60.degree. with the circumferential direction of the tire, and a ply of metallic elements oriented substantially parallel to the circumferential direction, arranged radially between the two working crown plies.
U.S. Pat. No. 4,688,615 describes a crown reinforcement for a radial tire composed of a first ply and of a second ply formed by cables parallel to each other in each ply, crossed from one ply to the next, forming an angle with the circumferential direction of the tire that can range between 5 and 60.degree.. A third ply of circumferentially arranged cables is placed between said two plies, said cables having a diameter at most equal to the diameter of the cables of the first and second plies, and being made of a material having a tensile strength less than the tensile strength of the material forming the cables of the first and second plies, which imparts a lower tensile strength to said third ply, and being more extensible than each of the plies with crossed cables, said third ply being no wider than the ply of cables with the widest angle.
The object of such an architecture is to reduce the operating temperatures prevailing at the edges of the working plies, the width of the additional ply of circumferential cables being less than the widths of the working plies.
Since the reduction of the operating temperatures in tires is also a major concern of the manufacturers of heavy truck tires, whatever the H/S form ratio, the Applicants' research has led them to look for a solution which is both effective and economic.